Modification of cellulose with amino compounds: A fluorescence study

Celluloses treated with amino compounds such as polyethylenimines and ethylenediamine show a noticeable fluorescence which depends on the thermal history of the material. Samples of cellulose were treated with polyethylenimine and ethylenediamine in aqueous solutions and subjected to thermal treatments in order to study the fluorescence and obtained information about the chemical transformations that take place in the modified celluloses. To elucidate the nature of the fluorophores existing in the treated cellulose, the fluorescence of model compounds obtained in the reaction of polyethylenimine with acetaldehyde was also measured. The products of this reaction and the modified celluloses were characterized using FTIR and UV–vis spectroscopic techniques. The analysis of the results indicate that the amino groups react with carbonyl groups present in the modified celluloses to form conjugated imines, which are responsible for the observed fluorescence.